Currently, there is a steady increase in the incidence of diabetes mellitus (DM) in the global population, which causes an increase in maternal and perinatal mortality. Children born to mothers with DM have a high risk of not only congenital abnormalities, but also cardiovascular and metabolic disorders in later life. Fetal growth is determined by both the metabolic and nutritional status of the mother, and the placental nutrient transfer capacity. Pregnancy complicated by DM is associated not only with overgrowth of the fetus, but also with the excess deposition of metabolites in the placenta. The role of disorders of carbohydrate metabolism, obesity and other factors in relation to the function of the placenta and fetal growth remains not fully understood. This review provides an overview of the literature on the placental complex status in pregnancy complicated by obesity, as well as pre-gestational and gestational types of DM. The focus is on three key substrates in these conditions: glucose, lipids, and amino acids, and their influence on placental metabolic activity and on the fetus. Improved knowledge of morphology and understanding of changes in the function of the placenta that lead to abnormal growth of the fetus will allow for the development of new therapeutic approaches to improve the outcomes of pregnancy, maternal and child health.

25ОРИГИНАЛЬНЫЕ ИССЛЕДОВАНИЯ ТО М L X I I В Ы П УС К 6 / 2 0 1 3 ■ В статье описана роль фолиевой кислоты при беременности, а также негативные последствия дефицита фолатов у беременных. На основе анализа собственных данных показано превышение нормы концентрации фолатов в крови беременных, принимающих препараты, содержащие фолиевую кислоту. Указаны возможные побочные эффекты длительного повышения в крови содержания фолиевой кислоты. Даны рекомендации по оптимизации фолатной терапии при осложнениях беременности.■ Ключевые слова: беременность; фолиевая кислота; гомоцистеин; витамин В 12 .

Hypothesis/aims of study. Diabetes mellitus (DM) is associated with an increased risk of obstetric complications, including preterm birth (PB). The incidence rate of PB in women with DM is higher than in the general population and amounts to 3040%. Nevertheless, there are still open questions on the structure of PB, pharmacological approaches to its prevention and treatment, as well as the feasibility of prolonging the timing of glucocorticoid therapy to reduce perinatal morbidity and mortality. The objective of this study was to research the features of structure and clinical approaches in the case of PB in women with different types of DM, based on a literature review. Study design, materials and methods. The study was performed using literature search, screening, data extraction, and analysis of publications collected in world databases such as MEDLINE, EMBASE, CNKI, and Cochrane. Results. The rate of PB is the highest in women with pregestational DM: 2130% in type 1 DM and 1940% in type 2 DM. The incidence of PB in gestational DM (710%) is almost equal to the general population level (79%) and depends on the type of diabetes therapy: insulin 16%, diet 7%. Risk factors for PB in women with DM are poor glycaemic control, microvascular complications of DM, hypertension, obesity, infection, age, fetal macrosomia, polyhydramnios, and congenital malformations. Adequate glycemic control from early gestation is an important condition for PB prevention. The structure of PB in patients with pregestational DM changes due to an increase in both spontaneous and induced PB proportions. The most common indications for early delivery in DM are preeclampsia, premature placental abruption, impaired renal function in diabetic nephropathy, severe forms of carbohydrate metabolism disorders, diabetic fetopathy, and fetal distress. The risk of fetal respiratory distress syndrome in newborns of mothers with DM is higher than in the general population. The maturity of the lungs of a newborn may be insufficient, even in the case of term delivery. The use of antenatal corticosteroids is effective prophylaxis of respiratory disorders. However, these corticosteroids can increase the risk of neonatal hypoglycemia. Conclusion. Despite the term weight and height, the newborn of a mother with DM may remain immature, therefore, delivery at term is recommended. The gestational age, until which it is advisable to prescribe corticosteroids for pregnant women with DM, and the mode of delivery in the case of PB, remain a matter of debate.

Oxidative stress (OS) plays an important role in embryo development, implantation, placentation, fetal development and labour. Diabetes mellitus (DM) is associated with an increase in OS processes. However, the expression of OS biomarkers in pregnant women with DM remains unclear. Based on a literature review, the features of the pro- and anti-oxidant systems of pregnant women with different types of DM have been established. Pregnancy in patients with DM has been shown to be characterised by an activation of OS processes. This leads to an overexpression of free radicals (peroxynitrite), toxic derivatives (malonic dialdehyde, 8-isoprostane) and specific enzymes (asymmetric dimethylarginine, catalase) and a decrease in the synthesis of antioxidants (superoxide dismutase, glutathione peroxidase and uric acid). The modified expression of these biomarkers is observed both in the blood and the placenta of pregnant women. These disorders can cause an unfavourable course of pregnancy, abnormal development of the placenta and development of adverse perinatal outcomes in pregnant women with DM. Nevertheless, given the inconsistency of data obtained, further scientific studies are needed to clarify this issue.

Objective: on the basis of a systematic review, clarify the role of overweight and obesity as a predictor of gestational diabetes mellitus (GDM). Materials and methods: an analysis of the literature data of the leading bibliographic sources - MEDLINE, Cochrane col., EMBASE. To evaluate the body mass index and standards of weight gain during pregnancy used the WHO guidelines and criteria of the Institute of Medicine (2009). The frequency and the odds ratio (OR) of developing GDM was estimated separately for each of the three groups in BMI. Results: A systematic review included 23 different design studies involving 740 510 women. It was found that the odds ratio of the risk of GDM in a group of pregnant women with excess weight is doubled - 2.22 (95 % CI 1.72 - 3.64), and almost four in obesity - 3.88 (95 % CI 2.97 - 5.32). The incidence of GDM in a group of pregnant women with normal body mass index - 3.77 % in the group with excess body weight - 6.59 %, in the group with obesity - 9.88 %. Conclusions: The obtained strong evidence of a direct connection between the linear increase in maternal BMI and the risk of developing gestational diabetes. Pregnant women with excess weight and obesity are at high risk for carbohydrate disorders during pregnancy.